Designing window openings (in buildings) has always been challenging for architects. Meticulous techniques have been used for constructing Sash windows in the past. Analysis and assessing these methods can provide better cognition of these windows. As a result, new solutions are provided for contemporary architecture. Investigations on Sash windows only have been dealt with aesthetic and climate aspects, and the construction techniques and their details have never been investigated. This research has studied and classified different types of this particular window by introducing the structural features, for the very first time. The data in this article have been gathered by library studies and field observations of case studies in Iran. In this research, different types of Sash windows are introduced and classified; moreover, construction techniques of each type by providing details are presented. By analysing these windows, their importance will be revealed in the past. Furthermore, by analysing the applied details, new solutions could be obtained for further designs.